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SubjectRe: [PATCH 4/7] wifi: cfg80211: Annotate struct cfg80211_pmsr_request with __counted_by
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On 8/17/23 15:15, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct cfg80211_pmsr_request.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Johannes Berg <johannes@sipsolutions.net>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: linux-wireless@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
> include/net/cfg80211.h | 2 +-
> net/wireless/pmsr.c | 3 +--
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index 5c7d091b3925..e9ca4726a732 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -3948,7 +3948,7 @@ struct cfg80211_pmsr_request {
>
> struct list_head list;
>
> - struct cfg80211_pmsr_request_peer peers[];
> + struct cfg80211_pmsr_request_peer peers[] __counted_by(n_peers);
> };
>
> /**
> diff --git a/net/wireless/pmsr.c b/net/wireless/pmsr.c
> index 77000a264855..9611aa0bd051 100644
> --- a/net/wireless/pmsr.c
> +++ b/net/wireless/pmsr.c
> @@ -291,6 +291,7 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info)
> req = kzalloc(struct_size(req, peers, count), GFP_KERNEL);
> if (!req)
> return -ENOMEM;
> + req->n_peers = count;
>
> if (info->attrs[NL80211_ATTR_TIMEOUT])
> req->timeout = nla_get_u32(info->attrs[NL80211_ATTR_TIMEOUT]);
> @@ -321,8 +322,6 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info)
> goto out_err;
> idx++;
> }
> -
> - req->n_peers = count;
> req->cookie = cfg80211_assign_cookie(rdev);
> req->nl_portid = info->snd_portid;
>

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